Deciduous vs. Evergreen: Solutions for Flying Drones in Every Season

This is the third guest post from David Williams, founder of Northwest Drone Pros, in a series on best practices for flying drones around trees. The last post covered “in-flight tips“. David is an instructor in the free course, “Solar + Drones: Site Surveying and 3D Mapping Around Trees“.

When we talk about flying drones around trees, it’s crucial to understand the two types of trees. Deciduous and Evergreen. And each has their own unique challenges.

Deciduous

Deciduous trees are more likely to be effected by wind and with smaller branches and leaves it can be harder to see the danger even when the drone is 10 feet above the roof line and certainly so when its 70 feet above ground level so these are things you want to be aware of. We’ve all seen trees swaying in the wind and in my experience deciduous are more likely to have a greater amplitude of sway, and the higher up you go the more this becomes true.

Deciduous trees pose additional challenges to modeling because they don’t retain their leaves throughout the season. So the shade analysis will change throughout the year. When it comes to flying around them in months when they have no leaves you need to make sure to get the whole tree in frame so the model is as accurate as possible. Because of their sparseness and lack of density in the winter they can sometimes be overlooked as an impact to the model.

Evergreen

Evergreen Trees – Evergreens have a higher wind resistance and are less likely to sway at the amplitudes seen with deciduous so I feel much more comfortable getting the drone close to them and even occasionally splitting branches when necessary, but because of their height, the fact that once you breach them wind speeds are always higher and keeping your line of sight on your drone is much harder because of the density of their profile they are also challenging. But obstacle avoidance is much more likely to see an object with the robustness of an evergreen.

Seasonal Challenges

Being located in Northwest Washington, anytime its not raining is a good time to fly, but my recommendation is to always check the weather before driving out to a survey. Having to cancel after arriving and then return later is not only a waste of time but delays the project. My area is also prone to fog which is often at altitudes lower than the trees surrounding the survey and fog is hard to predict so if I am unfamiliar with an area or it is far away I like to survey in the afternoon when the fog has burned off. Too bright of sun can also pose issues especially with a white roof but unfortunately for us in the Pacific Northwest that’s rarely an issue.

Point of Interest

Point of Interest or POI as I mentioned in previous slides is a tool that will make your survey life much easier. The way it works is you set your point of interest and the drone maintains the speed, altitude and circumference set by you. If you have obstacle avoidance or Advanced Pilot Assistant Software you’ll want to make sure its enabled. POI is very intuitive and can be setup in seconds.

1. First you’re going to press the flight mode button on the left
2. Select Point of Interest as your flight mode
3. The POI Flight Mode Display will pop up
4. Once you are at an altitude higher than the tallest obstruction or tree and the full survey subject is in frame, using your finger you will drag the square around your point of interest and press go. At this point a warning will pop up notifying you to “not operate the aircraft during subject position calculation” which usually takes only a few seconds. After that you can adjust your radius, height or speed if necessary and beginning taking images. If for any reason you need to exit this mode just hit the red x and the drone will hover in place.

You have a lot of things going on, you’re watching your 2 thousand dollar drone in the air, you’re making sure camera angle is right, you’re checking that the whole point of interest is in frame, you’re taking a picture every 2 to 3 seconds, you have trees swaying that are over 100 feet tall, the neighbors want to see what’s going on. So its best to aware of the dangers trees pose and have everything set right before liftoff. I hope I was able to give you some useful tips to keep in mind when flying around trees. My presentation was all about protecting the drone but the alternative is going up on the roof and risking injury and obviously the more times you do it the more likely injury is, so better the drone than you but hopefully my tips will help you protect it as well!

This is the third in a series of solar plus drones guest posts.

This series is an adaptation of the “Solar + Drones” webinar developed in partnership with Scanifly.